Which agent would you like to install for a WEB appliance

I'm currently designing a WEB appliance based on Linux and WebSphere Application Server, I would like to know which agent opensource or commercial would you install for this kind of appliance. logically we have to get get the following kind of metrics:

1) Linux performance.
2) Application Server performance.
3) Linux resources usage.
4) Application server resources usage.

What do you think ?